Children are more frequently suffering sporting injuries that are more typically seen in adults, according to a leading sports scientist.
David Epstein said that youth athletes were now sustaining injuries that would be more common later in life, and that in many cases they could go undiagnosed for a period of time.
The author of 'The Sports Gene' - a scientific examination of sporting ability - told the Irish Independent that this worrying trend was developing because "they are playing the same sport all year round for different teams".
"It's not just mental fatigue, but there are also injuries that used to be seen only in older athletes that are moving down in age," he said.
"So things like torn labrums in the hip, which sometimes a young athlete would not know what it is for a while - they are just having groin pulls or lower back pain.
"And other injuries that used to be only seen more in adult athletes, now we are seeing them in youth athletes.
"And that seems to be because they are playing the same sport all the year round for different teams."
The New York-based journalist spoke recently in Dublin at the Web Summit and in UCD.
He said his research had indicated to him that "kids don't need to play less sports overall, but that they need to be somewhat diversified".
"There actually seems to be a protective effect of diversifying your sports. They are being coached in a way that is more appropriate for adult athletes.
"The best way to learn sports skills is the way a baby learns a language. First they immerse and they play, and later teach them the technical points," he said.
Mr Epstein said that forcing a child to specialise in a sport at a young age "is not the way to go for health, or for skill development either".
"The typical path for future elite athletes is that they are actually doing less specialised practice in their future sport early on. And they focus in later," he added.
He said that he believed that when the child reached 12, it may then be appropriate for them to specialise in a particular field.
"It depends on the sport a little bit, but I think that all of the sports science agrees that there should be diversification, not focus on specialisation, until the age of 12 at least - that's a period where you have a lot of brain flexibility," the writer said.
"It's clear that they shouldn't be focused before 12 years old, and then after that it is a bit of an open question."
He said that intense, specialised training did not generally benefit the athlete in their later years.
"You might end up making the best 14-year-olds, but you are not going to make the best 24-year-olds," he commented.
"In the vast majority of sports, we now have some of these studies that have been done over a long period of time. And the typical path for future athletes is that they are actually doing less specialised practices in their future sport early on.
"The typical path is like Roger Federer, whose parents forced him to continue playing badminton, soccer and basketball before he focused on tennis," the 33-year-old Chicago native added.